The invention relates to a charging system for implantable hearing aids and tinnitus maskers with a repeatedly rechargeable direct voltage source.
Charging systems for the batteries of pacemakers are known, for example, from German Offenlegungsschrift No. 19 40 803 or U.S. Pat. No. 4,134,408. The process used in these systems for inductive power transmission is based on two coupled coils, similar to a transformer, one of the coils being implanted and the other coil being brought externally near the implanted coil. The implanted coil directly supplies, in a broadband way, a rectifier circuit. Because of the poor coil coupling, this type of power transmission allows only relatively limited charging currents for the battery. These were sufficient for the batteries of pacemakers since, for the operation of a pacemaker, only a small amount of power is needed, and thus, one can make do with limited battery ampere-hour capacities. In contrast, the operation of a hearing aid or a tinnitus masker has a significantly higher power requirement, since these devices are permanently active.
An implantable hearing device with a repeatedly rechangeable direct voltage source is known from German Patent 39 18 086 C1. But, the charging system for the direct voltage source is not explained there.